Motor questions

Describe the function of the capacitor in a capacitor start motor.

• Provide a phase shift in the auxiliary winding to produce high starting torque and is disconnected after the motor reaches speed

• Filter supply harmonics to improve line quality during running

• Increase the steady‑state power factor of the motor under normal operation

• Store DC energy to supply the main winding during starting

List 3 types of AC motor controller.

• Variable frequency drive (VFD)

• Soft starter

• Direct‑on‑line (DOL) starter

• DC chopper

State 2 types of single‑phase AC motor.

• Capacitor‑start induction motor

• Shaded‑pole motor

• Three‑phase squirrel‑cage induction motor

• DC shunt motor

Explain why star‑delta motor control equipment is used in preference to direct on line.

• To reduce starting current and mechanical stress compared with direct‑on‑line starting

• To automatically reverse rotation without additional wiring

• To increase starting torque beyond direct‑on‑line capability

• To improve full‑load efficiency of the motor during normal operation

What is the main advantage of using an autotransformer starter for induction motors compared to direct-on-line starting?

• It eliminates the need for overload protection

• It reduces the initial voltage applied to the motor, lowering starting current and mechanical stress

• It increases the full-load efficiency of the motor

• It reverses the direction of rotation automatically

What is the role of the centrifugal switch in a capacitor start motor circuit?

• It provides overload protection for the main winding

• It increases the running efficiency of the motor

• It reverses the direction of rotation during starting

• It disconnects the starting capacitor and auxiliary winding once the motor reaches a certain speed